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Building a Relational Data Model

In This Chapter

Building a Data Model

Overview of the Entity-Relationship Data Model

Identifying and Defining Principal Data Objects

Discovering Entities

Choosing Possible Entities

The List of Entities

Telephone Directory Example

Diagramming Entities

Defining the Relationships

Existence Dependency

Discovering the Relationships

Diagramming Relationships

Identifying Attributes

Selecting Attributes for Entities

Listing Attributes

About Entity Occurrences

Diagramming Data Objects

Reading E-R Diagrams

Telephone Directory Example

After the Diagram Is Complete

Translating E-R Data Objects into Relational Constructs

Defining Tables, Rows, and Columns

Placing Constraints on Columns

Domain Characteristics

Determining Keys for Tables

Foreign Keys (Join Columns)

Adding Keys to the Telephone Directory Diagram

Resolving Relationships

Resolving m:n Relationships

Resolving Other Special Relationships

Normalizing a Data Model

First Normal Form

Second Normal Form

Third Normal Form

Summary of Normalization Rules

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